With the aim of characterizing antigenically isolations producing mild cytopathogenic effect obtained from the cerebrospinal fluid of patients presenting with epidemic neuropathy, neutralization tests and western blot analysis were performed using hyperimmune sera of patients and hyperimmune sera of rabbits. It was confirmed that isolations with mild cutopathogenic effect studied have the same antigenic characteristics and that they are related to Coxsackie A9 and B4 viruses. Structural proteins were not detected in the strains with mild cytopathogenic effects, only antigens having a high molecular weight which were considered as precursor proteins for viral replication were confirmed.